Oil filter for internal combustion engines

ABSTRACT

The present invention relates to an oil filter (1) for internal combustion engines, which is preferably used in secondary oil circuit in addition to a conventional oil filter. The oil filter comprises a filter housing (2a, 2b, 3o, 3u) in which a filter element (5) that consists of a roll of absorbant paper that is wound about a rod (4) is installed. In order to simplify production and inventory management, the present invention proposes that the oil filter be configured as a set of elements that comprises the body sections (2a, 2b) and caps (3o, 3u) and a rod (4) with the rolled filter element (5). The volume of the oil filter can be matched to a particular application by connecting a plurality of body sections (2a, 2b) with an appropriate number of rods (4).

The present invention relates to an oil filter for internal combustionengines as set out in the defining portion of Patent claim 1.

Internal combustion engines are fitted with oil filters that arenormally flange-mounted onto the crank case of the engine. Such oilfilters remove only some of the contaminants that are contained in theoil that circulates within the engine.

DE-PS 1 051 062 describes an oil filter in which the filter element is aroll of absorbent paper, e.g., toilet paper, that is installed on acentral rod. Such oil filters act as fine filters and, in addition, canbe arranged in a secondary path of the engine oil lubrication system,i.e., they can be used in addition to existing oil filters. Thisprovides for significantly improved filtering action. Because of thisfine filtering action, for all practical purposes, it is unnecessary tochange the engine oil, and all that needs to be done is to replace theoil that has actually been used.

The principle underlying such oil filters has been widely developed. Theoil flows through the paper filter element between an inlet and anoutlet, in counter-flow, as in the abovementioned pat. specification orin accordance with EP-OS 262 596, or in a radial direction, as in thefilters described in DE-PS 24 60 073 and DE-GM 87 00 995. Filtersconstructed in a similar way are known and used for filtering, fuels,and these work on the straight-through principle, so that the fuel flowsthrough the wound-up filter element in an axial direction; see DE-OS 3617 420.

In order to achieve almost complete fine filtering of the oil, thevolume of the filter element must be matched to the total quantity ofoil circulating within the engine, to the rate of flow, and to the oilpressure. The greater these values, the greater will be the volume ofthe filter element. For this reason, conventional oil filters have to beproduced in various sizes, in order to provide a match to engines ofvarious sizes. This makes both production and inventory management morecostly.

It is the task of the present invention to describe an oil filter ofsimple construction that can be produced in a simple manner in varioussizes.

According to the present invention, this task has been solved by thedistinguishing features set out in patent claim 1.

Accordingly, the basic idea of the present invention is to provide suchan oil filter as a set made up of only a few individual parts, namely, abody section, end caps, and an extensible rod that supports a rolledfilter element, it being possible to connect the body sections and thecovers to form a closed filter housing.

The oil filter can operate on the straight-through principle, when theoil passes through the rolled filter element in an axial direction. Inthis case, the production units consist of a body section, a cover witha connector that serves as an inlet or an outlet, and an extensible rodproduced, for example, from solid material, onto which the filterelement is rolled. In addition, the counter-flow principle can also beused, in which the oil that is delivered to one cap first passes throughthe hollow rod and then through the filter element axially, in theopposite direction. In this instance, the production units are onceagain a wall section, one cap with an inlet and an outlet, an end cap,and a hollow rod that supports the rolled filter element. If the oilthat is to be filtered is meant to flow radially through the filterelement, then the hollow rod will be produced so as to incorporate theappropriate drillings.

The volume of the oil filter and the rolled filter element containedtherein can be made larger very simply in that a plurality of bodysections are connected to each other and a cap is used to cover off bothends. Connection of the individual parts is effected by interposing aseal that can be installed, for example, on a centering ring, possiblywith the help with bolted or clamped connections. A plurality of rodswith rolled filter elements are installed in the filter housing. By thismeans, it is possible to-influence the filter quality in that, forexample, the filter elements can incorporate various pore diameters forcoarse and fine filtering. To a very large extent, the danger of tracksforming [Roehrenbildung--Tr.] in the filter material has beeneliminated.

In addition, it is also advantageous to incorporate cooling ribs in thebody sections and, optionally, on the outer surfaces of the end caps,which will result in good thermal radiation and simultaneously cool theoil that passes through the oil filter.

Additional embodiments of the invention are described in the subclaims.

The present invention is described in greater detail below on the basisof the embodiments shown in the drawings appended hereto. These drawingsshow the following:

FIG. 1 a diagrammatic cross section through an oil filter according tothe present invention, this consisting of two body sections, twoidentically configured caps, and two rods, each of which supports arolled filter element;

FIG. 2 a cross section through a body section of the oil filter as inFIG. 1;

FIG. 3: a plan view of a cover of the oil filter as in FIG. 1;

FIGS. 4a to 4c: various configurations of rods for oil filters accordingto the present invention;

FIG. 5: a cross section through a pressure valve for use in connectorsused for oil filters according to the present invention;

FIG. 6: a diagrammatic representation of an oil filter in which the bodysections and the covers are connected to each other or together with thehelp of annular clamps;

FIG. 7: a plan view of such an annular clamp;

FIG. 8: a diagrammatic view of an oil filter in which the wall sectionsand the covers are connected to each other or together by means ofbolted connections;

FIGS. 9a and 9b: a transverse section or plan view, respectively, of acentering ring that can be inserted between two body sections o f an oilfilter that are to be joined, together;

FIGS. 10a, b, and c: a diagrammatic representation of connectors betweenan engine and an oil filter according to the present invention.

FIG. 1 shows an oil filter 1 that comprises two cylindrical bodysections 2a and 2b, an upper and a lower cap 3o or 3u, respectively, andtwo rods 4 that are of solid material, there being a filter element 5 ofabsorbent paper wound onto each such rod. The cylindrical body sectionsincorporate seating surfaces 6 for a seal 7, e.g., an O-ring, on both oftheir opposing peripheral edges, the covers 3o and 3u incorporatingsimilarly configured seating surfaces, for example, on the bottom of agroove 8.

The body sections 2a and 2b incorporate a plurality of flange lugs 9 atboth of their ends, in this case three such flange lugs (see FIG. 3),with which the flange lugs 10 on the caps 3o and 3u are associated. Thebody sections 2a and 2b are joined together or to the caps 3o and 3uthrough these flange lugs 9 or 10, respectively, by means of bolts 11,with O-rings 7 interposed between them.

Instead of installing only an O-ring or another seal between the twobody sections 2a and 2b, in order to simplify assembly, it can also beexpedient to install a centering ring 12 between the body sections, thisthen enclosing the two body sections on their outer periphery, andincorporating a T-piece that extends radially inwards, O-rings 7 orother seals being installed on both sides of this, on which the seatingsurfaces 6 of the two body sections 2a and 2b then rest. This O-annularclamp is shown clearly in FIGS. 9a and 9b.

The identically configured body sections 2a and 2b incorporate coolingribs 21 that are distributed about their periphery and these extend tothe whole axial length of the body sections. Additional connectors 22that incorporate a hollow T-cross section 23 are provided at least ontheir upper and lower edges, and the oil filter can be secured to acorresponding T-bar or T-bar section on the vehicle body with these. Theoil filter can be slid along this T-bar during installation.

The two identically configured caps 3o and 3u each incorporate a centralscrew connector 31 that serves as an inlet or outlet for the oil that isto be filtered. In addition, as is shown by the dashed line in FIG. 1,an air bleed 31' can also be incorporated. The outer side of the cap 3o,3u incorporates radial cooling ribs 32. A distance piece 33, forexample, a metal net or an appropriate pattern of ribbing is installedon the inner side of the caps.

On the one hand, this distance piece serves to keep a specific distancebetween the inner opening of the screw connector 31 and the rod 4 and,on the other, to distribute the oil that enters through the screwconnector 31 over the whole surface of the filter element 5, or else toprovide a path for the oil that leaves the overall surface of the filterelement 5 to the screw connector. On the inner side of the cover 3o, 3uthere is also a circular flange 34 close to the inside periphery of thebody casings 2a and 2b. The tapered edge 35 of this flange, which is,for example, of triangular cross section, fits into the rolled filterelement 5. Any leakage of unfiltered oil between the outer wall of thefilter element and the inner wall of the body casing is interrupted bythis flange, so that the leakage oil still has to flow through thefilter element before it can leave the oil filter. However, such leakageis, for all practical purposes, precluded, since the filter element liestightly against the inner wall of the body sections.

The filter element 5 of absorbent paper is rolled around the rod 4,which thus fills all of the space between the rod and the inner wall ofthe body sections. A plurality of such rods can be connected to eachother; in the case of the oil filter shown in FIG. 1 there are two suchrods, and an additional distance piece 33 can be installed between twofilter elements in the area where the body sections are connected toeach other.

FIG. 4a shows a rod 4a that is of plastic, for example. At one end, therod 4a incorporates an insertion hole 41a, and, at the other end, aninsertion peg 42a. Thus, two rods can be joined to each other through apush connection 44a. In FIG. 4b, a screw connection 44b serves tolengthen the rods 4b with the rolled filter elements, each rod 4bincorporating a thread 41b at one end, and a threaded peg 42b at theother end.

FIG. 4c shows two hollow rods 4c, each of which has a thread 41c and athreaded peg 42c, these being connected together by means of a screwconnection 44c. Such hollow rods are used if the oil filter is notintended to operate on the straight-through principle as in FIG. 1, butaccording to the counter-flow principle. The oil then flows from thecentral inlet 31 through the hollow rod down to the opposite end of theoil filter, which is closed off at this point by a cap. The oil thenflows in an axial direction over the distance piece or distributor ofthis end cap and back through the filter element 5, is stopped in thedistance piece or distributor 33 of the lower cap, and there diverted toan outlet. This outlet is shown by means of the dashed line in FIG. 1and is numbered 31". The hollow rod 4c can also incorporate drillings 45(only indicated herein) along its whole length, through which the oilthat is to be filtered flows out radially into the filter element.

FIG. 5 shows a check valve 51 that can be screwed into the screwconnector 31 of an oil filter. The check valve incorporates a ball 52 asthe valve body and this is supported by a spring and retained by a ring54. The spring 53 is so dimensioned that the oil can only flow into theoil filter in the direction indicated by the arrow once a specificpressure has been reached. This pressure valve serves essentially toensure that when the oil filter that has been described is installed ina secondary oil path, it is fully supplied with oil that flows from themain engine-lubrication system when the engine is started. Optionally,this pressure valve can also be used as a pressure relief valve, forexample, by appropriate matching of cross section of the continuousdrillings of the hollow rod shown in FIG. 4c, so as to ensure that oilis not forced through the oil filter at an excessive pressure.

FIG. 6 shows the connection of body sections and end caps of an oilfilter, by means of annular clamps 61. On their outer peripheral edges,these body sections and covers incorporate a bead 62 or a circularflange. An O-ring 7 or an annular washer is inserted between the flangesof the body sections that abutt against each other. The outer edges ofthe beads are enclosed by a spring band 63 that is connected rigidly toan annular clamp housing 64. Between the annular clamp housing 64 andthe outer curved end of the spring band there is a plurality of metalrods 65 arranged about the periphery of the annular ring. This ensuresthat the spring band 63 cannot be deformed outwards. The annular ringcan be closed in the usual manner with a screwed joint 66 or a clip. Thesprung metal rods that lie securely between the ends of the spring bandand the inner periphery of the annular clamp housing 64 when the annularclamp is closed ensure great application force on the body casings ortheir beads, without any essential deformation forces being transferred.This ensures a tight connection even at high oil pressures.

FIG. 8 shows a part of an oil filter with two body sections 2a and 2band an upper cap 3o. The body sections incorporate threads 71 on theirouter edges and the interior thread of a lip 72 of the cap 3o fits inthis thread. The two body sections 2a and 2b are connected to each otherby means of a threaded ring 73 that fits into the threads of theadjoining body sections 71. An O-ring is installed between the bodysections in the area of this screwed joint. It is also possible toprefabricate the body sections with the filter element so that when afilter element is renewed, the body section with the used filter elementis removed and replaced by a new part. It is also possible toprefabricate an oil filter from body sections, caps, and a filterelement and when the filter element is renewed, replace the whole filterunit. When such prefabricated filter cartridges with a large filteringvolume are required, it is necessary to incorporate a plurality ofcomplete filters in series.

If the oil filters described heretofore are used on the straight-throughprinciple, it is not necessary that the filter element contain a rod.The filter element is, for example, of pressed material such as toensure that no bypass channels or leakage channels exist in it.

In order to connect the oil filter described heretofore in a secondarypath to an engine, the connector elements 81, 82, and 83 as shown inFIGS. 10a, b, and c are provided. The connector 81 is screwed into theengine block with a threaded connector 84 in place of the oil pressuregauge sender unit. A central drilling 85 leads to an internal receivingdrilling 86 in which a thread 87 of the connector element 83 is screwed,with the connector element 82 being interposed between them. Theconnector element 83 has a central drilling 88 from which a transversedrilling 90 branches off in a step 89; when the three connector elements81, 82, and 83 are screwed together, the connector 82 is located in thearea of the step 89. Then, oil can be tapped off from the transversedrilling 90 into a drilling 91 of the connector that leads to theabove-described oil filter.

Then, the existing oil pressure gauge sender unit is screwed into aninternal drilling 92 in the connector 83.

I claim:
 1. An expandable elongate oil filter, for an internalcombustion engine, said oil filter comprising:first and secondcylindrical body sections concentrically aligned about a common axiseach defining a hollow cylindrical interior housing a filter element,each of said first and second cylindrical body section having first andsecond opposed open ends, a seat located on axially facing edges of eachof said first and second open ends, each of said seats accommodating asealing means: each of said first and second cylindrical body sectionscontaining a central rod located along said common axis, and a saidfilter element, for filtering oil, located around the central rod, saidfilter element having an axial length corresponding to an axial lengthof its associated cylindrical body section and a diameter correspondingto an inside diameter of its associated cylindrical body section; thecentral rod of the first cylindrical body section and the central rod ofthe second body cylindrical body section each having means forconnecting the central rods end to end with one another; two end caps,each provided with a seat for accommodating a said sealing means of anassociated body section; means defining an oil inlet in one of said endcaps and means defining an oil outlet in one of said end caps; means fordirecting oil from said oil inlet to an inlet side of said filterelements, and means for directing oil from an outlet side of said filterelements to said oil outlet; first connecting means, independent of thecentral rods and completely external of the hollow cylindrical interior,for fixedly connecting said first open ends end to end with one another,second connecting means for fixedly connecting a first of the two endcaps to said second open end of said second cylindrical body section,and third connecting means for fixedly connecting the second of the twoend caps to said second open end of the second cylindrical body section;whereby a filtering capacity of the oil filter can be varied by varyingthe number of cylindrical body sections, central rods and filterelements interconnected between the first and second cylindrical bodysections.
 2. An oil filter according to claim 1, wherein each of thecylindrical body sections has cooling ribs provided on an exteriorsurface thereof.
 3. An oil filter according to claim 1, wherein the twoend caps each having cooling ribs provided on an exterior surfacethereof.
 4. An oil filter according to claim 1, wherein the firstconnecting means includes bolts interconnecting flange lugs attached toan external peripheral surface adjacent the seats on said first openends of said first and second cylindrical body sections, and the secondand third connecting means includes bolts interconnecting flange lugsattached to a periphery of said end caps with flange lugs attached to anexternal peripheral surface adjacent the seats on the second open endsof said first and second cylindrical body sections.
 5. An oil filteraccording to claim 1, wherein the first, second and third connectingmeans are annular clamps that fit around mating flanges formed on anexterior peripheral surface adjacent the seats on the first and secondopen ends of said first and second cylindrical body sections and formedaround a periphery of the two end caps.
 6. An elongate oil filteraccording to claim 1, wherein each central rod is a solid rod and eachfilter element is a roll of absorbent paper which fills the spacebetween the solid rod and an inner wall of the associated cylindricalbody section.
 7. An oil filter according to claim 6, wherein the two endcaps each have, on an inner surface thereof, a circular flange orientedaxially of said cylindrical body sections that engages the filterelement adjacent an outer edge thereof.
 8. An oil filter according toclaim 1, wherein each central rod is a hollow rod fluidly connected tosaid oil inlet, said hollow rod incorporating a plurality of drillingsspaced along the length of the hollow rod, the drillings extendingradially of the hollow rod and facilitate the flow of the oil radiallyoutward into the associated filter element.
 9. An oil filter accordingto claim 1, wherein said means for forming an oil inlet and said meansfor forming an oil outlet are internally threaded connectors provided inone of the two end caps.
 10. An oil filter according to claim 9, whereina check valve is connected to the connector for forming the oil inlet.11. An oil filter according to claim 1, wherein the sealing meansadjacent the seats of the first open ends includes a centering ringinstalled between the first and second body cylindrical body sections,the centering ring surrounds an outer periphery adjacent the seats ofsaid first open ends of the first and second cylindrical body sectionsand includes a portion which extends radially inward between adjacentseats of the first open ends of the first and second cylindrical bodysections, a said sealing means, supported by a said seat of the firstcylindrical body section, engages one side of the radially inwardlyextending portion, and a said sealing means, supported by a said seat ofthe second cylindrical body sections, engages an opposite side of theradially inwardly extending portion.
 12. An oil filter according toclaim 1, wherein a plurality of additional cylindrical body sections areinterconnected end to end between the first open end of the firstcylindrical body section and the first open end of said secondcylindrical body section, and said plurality of additional cylindricalbody sections each have a central rod and a filter element associatedtherewith.
 13. An oil filter according to claim 1, wherein means forbleeding air from the oil filter is provided in one of the two end caps.